Year	Percent
1960	24.39586
1961	20.10753
1962	17.12259
1963	18.72727
1964	19.49838
1965	17.87176
1966	12.84585
1967	10.30585
1968	11.11765
1969	11.7941
1970	14.16556
1971	14.12
1972	7.1048
1973	9.02599
1974	13.04721
1975	12.72005
1976	8.88753
1977	11.06333
1978	5.37501
1979	6.53745
1980	5.62401
1981	4.57274
1982	3.37764
1983	3.74977
1984	6.87682
1985	9.57009
1986	9.36208
1987	10.43405
1988	11.29599
1989	13.20901
1990	14.444
1991	15.87899
1992	12.8
1993	22.21017
1994	23.95773
1995	20.02141
1996	21.2
1997	24.80621
1998	23.10939
1999	21.00053
2000	23.9986
2001	26.59942
2002	19.7
2003	22.93693
2004	28.37751
2005	29.00214
2006	22.95412
2007	15.38454
2008	16.49196
2009	16.43179
2010	13.10019
2011	12.80999
2012	16.96772
2013	13.27997
2014	18.84557
2015	16.71246
2016	14.4871
2017	16.05857